Topical Esomeprazole Mitigates Radiation-Induced Dermal Inflammation and Fibrosis

Abstract

Radiation therapy is a mainstream strategy in the treatment of several cancer types that are surgically unresectable. Unfortunately, cancer patients often suffer from unintended consequences of radiotherapy, including the development of skin inflammation (dermatitis), which may progress to fibrosis. These morbid complications often require interruption of radiotherapy and threaten the relapse of underlying cancer. Current treatment options for radiation dermatitis are suboptimal and compel the need to develop safer, more effective therapies. In this study, we assessed the biophysical properties of topically-formulated esomeprazole (here referred to as dermaprazole) and performed proof-of-concept studies to evaluate its efficacy in vitro and in vivo. We found that dermaprazole induced nuclear translocation of erythroid 2-related factor 2 (Nrf2) and significantly upregulated heme oxygenase 1 (HO1) gene and protein expression in a 3D human skin model. Our animal study demonstrated that dermaprazole improved macroscopic appearance of the irradiated skin and accelerated healing of the wounds. Histopathology data corroborated the photographic evidence and confirmed that both prophylactically and therapeutically administered dermaprazole conferred potent anti-inflammatory and antifibrotic effects. Gene expression data showed that dermaprazole downregulated several pro-oxidant, pro-inflammatory and profibrotic genes. In conclusion, topical formulation of the FDA-approved drug esomeprazole is highly effective in attenuating dermal inflammation and fibrosis.

FIG. 1.

Regulation of the NOS/DDAH pathway by PPIs. PPIs directly inhibit DDAH enzymatic activity resulting in accumulation of the endogenous substrate ADMA. ADMA is a competitive NOS inhibitor and limits the production of reactive oxygen and nitrogenous species resulting in reduced tissue inflammation and fibrosis. Physiologically, oxidation of L-arginine in the presence of NOS generates nitric oxide. iNOS = inducible nitric oxide synthase; DDAH = dimethylarginine dimethylaminohydrolase; ADMA = asymmetric dimethylarginine; PPIs = proton pump inhibitors.

FIG. 2.

Gene expression profiling of the transcription factor erythroid 2-related factor 2 (Nrf2) and the antioxidant enzyme heme oxygenase 1 (HO1) in irradiated EpidermFT tissue homogenates from a 3D human skin model. The EpidermFT was exposed to various strengths of dermaprazole, vehicle cream or the steroid hydrocortisone (1%) for 24 h. Fold change normalized to the vehicle control is shown. Data are from duplicate experiments. *P < 0.05 compared to the expression of Nrf2 in the vehicle and +P < 0.05 compared to the expression of HO1 in the vehicle group.

FIG. 3.

Western blot analysis of erythroid 2-related factor 2 (Nrf2) and heme oxygenase 1 (HO1) proteins in homogenates derived from irradiated EpidermFT tissues. Nuclear and cytoplasmic proteins were fractionated and Nrf2 was probed in the nuclear fraction using rabbit anti-Nrf2 antibody. The housekeeping gene histone H3 was probed using rabbit anti-histone H3 antibody. HO1 was probed in the cytoplasmic fraction using rabbit anti-HO1 and GAPDH was detected using mouse anti-GAPDH antibody. The secondary antibody used was anti-rabbit monoclonal or anti-mouse monoclonal. The data show that dermaprazole upregulated the protein expression of Nrf2 and HO1.

FIG. 4.

Western blot analysis of heme oxygenase 1 (HO1) protein in homogenates derived from nonirradiated EpidermFT tissue. Dermaprazole (1–2%) was applied on the tissue topically and the viable EpidermFT tissue was incubated at 37°C/5%CO₂ for 24 h. HO1 was probed using rabbit anti-HO1 and GAPDH was detected using mouse anti-GAPDH antibody. The secondary antibody used was anti-rabbit monoclonal. The data show that dermaprazole upregulated HO1 expression in the absence of radiation.

FIG. 5.

Topical application of the PPI esomeprazole improves skin appearance in a fractionated radiation-induced model of dermatitis. Mice were irradiated (2 × 15 Gy) on days 0 and 7. Topical esomeprazole (i.e., dermaprazole), vehicle (base) cream or the corticosteroid hydrocortisone was applied once daily on the indicated days (days 1–30 for the prophylactic group and days 10–30 for the therapeutic group). Representative images from the same animals are shown.

FIG. 6.

Histological data showing that dermaprazole improves skin histology in a radiation dermatitis model. Panel A: H&E stained irradiated skin tissue from animals treated with vehicle cream, dermaprazole or hydrocortisone once daily on the indicated days. Panel B: Masson’s trichrome stain was used to assess the degree of dermal fibrosis. Increased collagen deposition (blue stain) is observed in the vehicle and steroid groups. Treatment with dermaprazole inhibited collagen deposition. Representative images are shown at 20× magnification. The scale bar shown in the vehicle group at day 16 is 50 03BCm and applies to all the images.